This invention relates to an apparatus and method for fatigue testing a vehicle wheel, such as is required of high performance racing wheels.
Fatique testing of vehicle wheels is frequently performed by wheel manufacturers to ascertain the number of revolutions the wheel can withstand before failing when a predetermined moment is applied to the wheel. Many of the organizations which govern a particular type of racing set standards for fatigue testing which must be met by a manufacturer's wheels before they can be used in that type of racing.
In the past, machines for fatigue testing vehicle wheels have simulated the action of the wheel on the vehicle. The wheel is mounted to a plate and a predetermined moment is exerted on the plate through a shaft mounted to the plate. The wheel is then spun about an axis coincident with the longitudinal axis of the shaft, which replicates stresses experienced by a wheel as mounted to a vehicle during operation of the vehicle.
The present invention provides an apparatus and method for fatigue testing a vehicle wheel, which also simulates the stresses experienced by a wheel as mounted to a vehicle. In direct contrast to the known testing procedure and apparatus, however, the present invention maintains the wheel stationary during testing. This allows the wheel to be observed and monitored during the test, which may reveal to the manufacturer certain areas of weakness in the wheel not detectable during a test in which the wheel is spun.
In accordance with the invention, an apparatus for fatigue testing vehicle wheel comprises wheel support means for maintaining the wheel stationary, and fatigue stress inducing means connected to the wheel for inducing stress in the wheel so as to simulate stress induced in the wheel when the wheel is mounted to a vehicle.
The wheel support means includes first support means engageable with one side of the wheel inwardly of a first lip of the wheel, and second support means engageable with the other side of the wheel inwardly of a second lip of the wheel. The first and second support means cooperate to fix the vertical and lateral position of the wheel on the apparatus during testing. The first support means comprises wheel supporting plate member which is preferably dimensioned so as to fit within the interior of an outwardly facing recess defined by the first lip of the wheel. A clamping assembly is provided for clamping the lower lip of the wheel to the wheel supporting plate member. The second support means preferably comprises a series of radially spaced clamping assemblies engageable with the wheel adjacent the upper lip of the wheel. In one embodiment, each clamping assembly comprises a lower support plate engageable with an inner surface of the wheel adjacent the upper lip of the wheel, and a threaded clamping member movable toward and away from the lower support plate and engageable with an outer surface of the wheel adjacent the upper lip. Each clamping assembly is preferably mounted to a collar member, which is mounted for vertical movement to a post. The collar members are provided with locking means for selectively fixing their vertical position on the posts.
The fatigue stress inducing means comprises a stress plate to which the wheel is bolted by means of bolt-receiving openings provided in the wheel, and a non-rotatable shaft extending from and interconnected with the stress plate. At least a portion of the shaft is mounted to a lateral loading assembly, which is rotatable relative to the shaft. The lateral loading assembly exerts a force on the shaft in a direction other than in line with the longitudinal axis of the shaft, and preferably in a direction substantially perpendicular thereto. In a preferred embodiment, the lateral loading assembly comprises a bearing member into which at least a portion of the shaft extends, lateral loading means exerting a lateral force on the bearing member which causes the bearing member to move laterally relative to the shaft, and means for imparting rotation to the bearing member when the lateral force is exerted on the bearing member. When the lateral force is exerted on the shaft and the lateral loading assembly is rotated, the shaft is caused to "wobble", which action is transferred through the shaft to the stress plate. Wobbling of the stress plate simulates the relationship of the wheel to a vehicle when the wheel is mounted to the vehicle and the vehicle is operated. The lateral force on the shaft is continuously exerted while the lateral loading assembly rotates so that, in time, the wheel fails due to fatigue loading. Based on the number of revolutions of the lateral loading assembly, the wheel manufacturer can determine whether the wheel conforms to the desired standards.
In a preferred embodiment, the lateral loading assembly comprises a bearing member mounted for slidable lateral movement within a carriage assembly. The carriage assembly is connected to the rotation imparting means for rotating the bearing member. A fluid-operated cylinder assembly is mounted to the carriage assembly, which is operable to selectively exert a lateral force on the bearing assembly. The exertion of a lateral force on the bearing assembly causes the bearing assembly to slide laterally within the carriage assembly, and to laterally deflect the portion of the shaft connected to the bearing assembly due to yielding of the wheel. In a particularly satisfactory construction, fluid pressure is supplied to the fluid-operated cylinder assembly through an internal passage provided in a shaft to which the carriage assembly is connected. A motor or the like is connected to the shaft for imparting rotation thereto, which is transferred through the shaft to the carriage assembly. A conduit extends between the shaft adjacent the carriage assembly and the fluid-operated cylinder for supplying fluid pressure to the cylinder.
Disabling means is preferably provided for disabling the apparatus when a predetermined amount of deflection of the shaft occurs, which corresponds to failure of the wheel.
In the preferred embodiment as described above, the fatigue stress inducing assembly is connected to the wheel and depends from the wheel. Counterweight means is preferably provided for offsetting the weight of the fatigue stress inducing assembly to reduce the effect thereof on the wheel during testing. As summarized above, the fatigue stress inducing assembly includes a stress plate to which the wheel is mountable. The wheel preferably includes a substantially central opening, and the counterweight means includes means for exerting an upward force on the stress plate through the opening in the wheel, with the upward force offsetting the weight of the fatigue stress inducing assembly. In one embodiment, a lug is mounted to the plate and extends through the opening in the wheel, and the upward force is exerted on the plate through the lug. The upward force exerting means includes a cylinder assembly having a movable piston, which is connected to the lug through a flexible connector member, such as a chain or cable. Retraction of the piston results in an upward force exerted on the lug through the chain or cable.
The invention also contemplates a method of fatigue testing a wheel, substantially in accordance with the foregoing description.